Aims and objectives
For intra-oral (IOR) radiography the radiation dose in the primary beam is typically a few mGy at the end of the collimator.
When this primary beam interacts with the patient’s head,
radiation will be scattered in all directions[1].
Whilst this represents a relatively low radiation dose compared to that of the primary X-ray beam this can often constitute a dose which operators can receive whilst performing radiography in the absence of a barrier.
Even though scattered radiation travels in all directions,
a greater proportion will...
Methods and materials
The experimental set-up used a Planmeca Intra X-ray Unit operating at 70kVp (as recommended by the manufacturers) rectangular collimation; anthropomorphic phantom and ionization chamber to measure scattered radiation dose.
Equipment Specifics:
Anthropomorphic phantom (DXTTR III),
consisting of a human skeleton within synthetic tissue equivalent.
Solid state scatter detector
Planmeca Intra X-ray Unit™
Generator – constant potential,
operating frequency 66kHz
Focal spot size – 0.7mm
Cone diameter – 60mm (rectangular 33x43mm)
Total filtration – 2mm Al equivalent at 70kV
Inherent filtration – 1mm at 70kV
The...
Results
At 50cm from the patient,
scattered dose ranged from 45.2-124.3µSv/hr.
At the edge of the controlled area (1.5m),
dose was highest (15.9µSv/hr) at point B in the forward scatter direction (aligned with the central ray).
Lowest scattered doses were measured behind the X-ray tube at point F and at point D which represents a position at 90o to the central X-ray beam. Here each position registered a dose measurement of 9.4µSv/hr.
Interestingly,
the next highest doses measured were at points E and G (14.9 and...
Conclusion
The spatial distribution of scattered radiation with the patient in the erect position was not the same in eight directions around the patient.
Although the preferred position for the operator is behind a suitable barrier when undertaking IOR,
the recommended position in the absence of a barrier,
based on experimental results during this study,
should be directly behind the X-ray tube.
This position represents a possible reduction in dose to the operator of 59% when compared to that recorded at the point of the exiting...
References
1 - de Haan,
R.
A.,
and J.
van Aken.
(1990) Effective dose equivalent to the operator in intra-oral dental radiography.
Dento-Maxillo-Facial Radiology 19:113-8.
2 - Cloke,
D.T.
and Vosper,
M.
(2007) Principles of Radiological Procedures 6th Edition,
Elsivere.
3 - Kuroyanagi K,
Hayakawa Y,
Fujimori H,
Sugiyama T.
(1998) Distribution of scattered radiation during intraoral radiography with the patient in supine position.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. Jun;85(6):736-41.